T.20A How does the voice quality compare versus the Rockwell chipset?

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Kolja Waschk (kawk@Yo.COM) writes:
"Rockwell chipsets do higher quality voice replay. This may be due to the fact
that they use a slightly more complicated ADPCM enconding or due to the fact,
that - in addition to ZyXEL modems - Rockwell chipsets are capable of
encoding the signal using 4 bits per sample. However, the RW chipsets do the 
sampling at 7200 Hz, the ZyXELs do it at 9600 Hz; that make me believe that 
the quality difference depends mostly on the coding algorithm (and tables) 
used.  On ZyXEL modems, it's nearly impossible to record voice without any 
digitally generated background noise; on those Rockwell equipped modems 
which I have seen (heard), it IS possible."

Top Document: ZyXEL modem FAQ List v4.2, Nov 20 1995, Part 3 of 5 [Technical FAQs]
Previous Document: T.20 How good is the voice quality?
Next Document: T.20B When will better quality speech at higher encoding rates be available?

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